Furnace construction



y 9, 1940- G. DANFORTH, JR 2,266,944

FURNACE CONSTRUCTION Filed March 9, 1940 3 Sheets-Sheet 1 3 a Q k 3 1 Nm 3 I i I J IN}:

IN VENT OR.

y 9, 1940- G. L. DANFORTH, JR 44 FURNACE CONSTRUCTION Filed March 9,1940 3 Sheets-Sheet 2 INVENT OR.

y 9, 1940- G. DANFORTH, JR 6,944

FURNACE CONSTRUCTION Filed March 9, 1940 3 Sheets-Sheet. 5

INVENTOR.

ATTORNEYS.

Patented July 9, 1940 UNITED STATES PATENT OFFICE Open Hearth CombustionCompany, 111., a corporation of Delaware Chicago,

Application March 9, 1940, Serial No. 323,079

8 Claims.

This invention relates to a new and improved furnace construction andmore particularly to the construction of the side walls or back wall ofa furnace of the open hearth type. The invention is directed to the wallconstruction above the metal line of the furnace or above approximatelythe line of the door sills and not to the walls of the hearth properwhich may be of any suitable and usual construction I01 supporting mboth the hearth and the walls of the present invention.

The present invention is not directed merely to the design orconstruction of the inner face of the wall but to the design andconstruction of u the entire wall including its protective covering ofbottom-making material and has especial reference to the form andconstruction of the outer face of the walls.

Furnace side or back walls were formerly built vertically and since itwas possible to protect only the base of the wall by means of thebottommaking refractory materials it was necessary to rebuild the upperportions of the walls at relatively short intervals. This rebuilding ofthe Walls was expensive both in cost of labor and materials and in lossof time in operating the furnace, due to the necessity of taking the gasoff the furnace and letting it cool down to some extent so that theworkmen could do the repairs.

, Later, sloping types of back walls were developed, as exemplified bythe constructions shown in the patent to Naismith No. 1,563,038, andthese walls have been widely adopted and have proven superior to thevertical walls. Nevertheless,

5 these have not entirely solved the problem as the upper portion of thewall has not been sufficiently protected. These sloping back walls arebased largely on the angle of repose of the bottom-making refractorieswhich it is intended to have lie up upon the wall. This angle is notconstant and therefore cannot be accurately predetermined, as thebottom-making refractories and their physical condition are subject tofrequent changes.

The span of the furnace roof must be increased to an extent equal to theoutward slope of the side wall. Too great an increase in the roof spanis undesirable. Therefore, the outward slope of the side wall asgenerally built approxi- 5 mates the average angle of repose, and issomewhat less than the maximum sometimes required by the variable natureor condition of the refractories used for maintaining the protectivelining, and at such times the inner face of the 55 upper portion of thesidewall becomes exposed and then burned away by the furnace flame. Asthe inner face is burned away it becomes flatter and is again covered bythe protective lining. After this has occurred a number of times, theupper portion of the wall is materially thinner and must then be renewedto the extent required, either by shutting down the furnace for repairs,or when the furnace is given a general relining.

If, instead of sloping the outer face of the wall as well as the innerface, the outer face is off- 1 set and substantially vertical, theexcessive thickness of the lower portions of the Wall insulates thecorresponding inner face to such a greater extent than the .upper facethat the lower portion is burned away and thereby destroys thefoundation orsupport for the protecting upper portion of the lining.

In constructing a side wall to use the Naismith invention, it has beencustomary to connect the full sloping portion to the vertical side wallsat the ends of the furnace hearth by gradually decreasing the slope ofthe wall to meet the vertical position. It isthen necessary to increasethe thickness of the furnace wall below the door sill elevation toprovide a foundation for the protective lining of bottom-makingrefractories, or else to gradually eliminate the protective lining.Either is undesirable, and therefore to the length of the connectingportion of the sloping wall, it is customary to change rather abruptlyfrom the full slope to the vertical position. This abrupt change formsan obstruction to the flow of the hot gases of combustion, which retardsthe flow of gases and wears away this portion of the wall and theadjacent portion of the furnace roof.

The construction of the present invention requires no greater lateraloifset of the top of the wall and consequently no wider roof than asloping back wall of the continuously sloping type of the Naismithpatent referred to above. It does, however, provide a more effectiveprotection to the wall than such prior types of walls. This isparticularly true as to the middle and upper portions of the wall and isaccomplished without the use of water coolers for the wall. 7

It is an object of the present invention to provide a. new and improvedside or back wall construction for furnaces of the open hearth type.

It is a further object to provide a wall construction for such furnaceswhich walls are of. substantially constant thickness and may comprisesubstantially uniform protective linings of refractory materialsthroughout a major portion of the height of the wall.

It is an additional object to provide a wall having its major brickportion extending outwardly and upwardly upon an angle to retain asubstantially uniform thickness of protective refractory material withthe upper brick portion of the wall vertical, said vertical portion alsobeing protected by refractory material.

It is also an object to provide a wall substantially fully protected byrefractory material and having no excessive wall thickness adjacent thedoor sill line or metal line of the furnace.

It is another object to provide a wall construction which mergesgradually with the end portions of the furnace without substantialchange in the angle of the sloping portion of the wall.

Other and further objects will appear as the description proceeds.

I have shown certain preferred embodiments of my invention in theaccompanying drawings,- in which- Figure 1 is a vertical section acrossthe center of the furnace;

Figure 2 is a plan view of half the furnace on a somewhat reduced scale;

Figure 3 is a fragmentary vertical section taken on line 3-3 of Figure2;

Figure 4 is a section similar to Figure 3 taken on line 4-4 of Figure 2;and

Figure 5 is a fragmentary section similar to Figure 3 but taken at thecenter of the furnace and showing a modified form of construction.

Referring first to Figures 1 and 2, the furnace is provided with ahearth portion ll, an end wall 82 and front and back walls l3 and Il,which walls are sometimes called side walls. The front wall is shown asextending vertically and provided with door openings l5. As shown inFigure 2, the furnace end includes the air uptakes l6 and I1, togetherwith the gas uptake it which is covered by the gas port structure [9. Asbest shown in Figure 1, the furnace hearth is provided with front andback walls 20 and 2|. These walls and the bottom 22 support the hearthlining 23 formed of refractory material. The tap hole 24 is shown asextending through the bottom-making material and the back wall 2|. Thefront walls are supported by the buckstays 25 and the rear walls by thebuckstays 26, the latter having the angularly offset portion 21. Thetops of these buckstays are held together by tie rods 28. The furnace isprovided with the arched roof 29 which spans the distance between thefront and back walls but does not rest on those walls, being supportedfrom the metal frame members 30 and 3| carried by the buckstays.

The rear wall of the furnace is provided with an outwardly and upwardlyinclined portion 32 which extends from approximately the door sill line33 up a substantial portion of the distance to the roof. To accomplishthe best results the outwardly and upwardly extending portion of theside wall should not be less than 40% nor more than of the total wallheight. Above the Wall portion 32 is erected a vertical wall section 34and this wall section conversely should preferably not be less than 20%nor more than 60% of the total height of the back wall or the totaldistance between the door sill line 33 and the skewback of the furnaceroof.

As clearly shown in Figure 1, the sloping wall portion 32 is at such anangle and is so related to the vertical portion 34 that it maintainsupon it a relatively heavy lining 35 of refractory material whichextends upwardly to the roof. This,

therefore, covers the wall portion 32 with a substantially uniform layerof bottom-making material and the greater portion of the vertical wallsection 34 is also covered with avery substantial thickness ofbottom-making The back wall is therefore fully and thoroughly protectedfrom hot gases by the bottom-making material. However, the entirethickness of the wall structure including the brickwork 32 and 34 andthe lining 35, is nowhere so excessive as to prevent suflicientradiation of heat- It is, therefore, unnecessary to supply watercoolers, which cause loss of heat from the furnace. The entire wall andthe protective are not substantially thicker at and adjacent the doorsill line than at the point of junction of the upwardly inclined andvertical wall sections. Consequently, any tendency to burn away at oradjacent the metal line and thus remove the support from the upperportion of the lining is The manner in which the sloping back is mergedinto the end sections is brought out in Figure 2 and in the twofragmentary sections Figures 3 and 4. The outwardly and upwardly slopingportion 32 of Figure 3 extends outwardly 25 on the same angle as doesthat portion of the wall at the center of the furnace, as shown inFigure 1. The side wall at this point, however, has less oifset so theportion 32 extends both. outwardly and upwardly a shorter distance andthe vertical wall section 34 is correspondingly taller. When the backwall reaches the pointindicated by the section lines H on Figure 2, theback wall 36 is vertical.

In Figure 5 is shown a. section taken on a center line of the furnace inwhich the combined thickness of the brick wall structure and fillnacelining is substantially the same as in the form of construction shown inFigure 1. In Figure 5, however, the wall I has outer face provided withan outwardly and upwardly extending portion ll and with a verticallyextending portion 42, while the inner face of the wall is on acontinuous slope as shown at 33. This, therefore, increasessubstantially the thickness of the brick structure at and adjacent theelevation of the junction of the upper and lower portions of the outerface. This brick structure of Figure 5 is, however, of the samethickness at the sill line and adjacent the roof skewback as the brickwall portion of the wall. structure of Figure 1. The refractory lining Nin the construction of Figure 5 is gradually tapered in thickness sothat the combined thickness of the lining and brickwork is substantiallythe same in the construction of Figure 5 as the combined thickness ofthese materials in the construction of Figure 1.

As compared with a wall of the type shown in the Naismith patent, on agiven furnace with the same offset and width of roof the presentconstruction provides a wall of more uniform thickness, greater strengthand less heat loss. If and when renewal or repair of the wall becomesnecessary, it would be confiend to approximately the top twenty percentof the present wall as compared with repairs to approximately fiftypercent of the wall of the prior art.

While I have shown certain preferred embodiments of my invention it iscapable of change to meet difl'ering conditions and requirements and Icontemplate such modifications as come within the spirit and scope ofthe appended claims.

What is claimed is:

1. In an open hearth furnace, a hearth, a roof, a side wall extendingfrom adjacent the door sill elevation to the roof, said wall having aninner surface extending outwardly and upwardly to retain a protectivelining of furnace bottommaking material substantially throughout thesurface, the wall having an outer surface extending outwardly andupwardly in its lower portion and substantially vertically in its upperportion.

2. In an open hearth furnace, a hearth, a roof, 2. side wall extendingfrom adjacent the door sill elevation to the roof, said wall having aninner surface extending outwardly and upwardly to retain a protectivelining of furnace bottommaking material substantially throughout thesurface, the wall having an outer surface extending outwardly andupwardly in its lower portion and substantially vertically in its upper'portion, said wall and the protective lining together havingsubstantially a normal thickness adjacent the base and the roof andhaving substantially greater than normal thickness at and adjacent theelevation of the junction of the upper and lower portions of the outerface.

3. In an open hearth furnace, a hearth, a roof, a side wall extendingfrom adjacent the door sill elevation to the roof, said wall having aninner surface extending outwardly and upwardly to retain a protectivelining of furnace bottommaking material substantially throughout thesurface, the wall having an outer surface extending outwardly andupwardly in its lower portion and substantially vertically in its upperportion, said wall and the protective lining together havingsubstantially normal thickness at the plane of the base of the wall andadjacent the roof, the protective lining having a substantially greaterthan normal thickness at and adjacent the elevation of the junction ofthe upper and lower portions of the outer face.

4. In an Open hearth furnace, a hearth, a roof, 3. side wall extendingfrom adjacent the door sill elevation to the roof, said wall having aninner surface extending outwardly and upwardly to retain a protectivelining of furnace bottom-making material substantially throughout thesurface, the wall having an outer surface extending outwardly andupwardly in its lower portion and substantially vertically in its upperportion, the lower portion of the wall constituting not less than fortypercent nor more than eighty percent of the height of the wall.

5. In an open hearth furnace, a hearth, a roof, a side wall extendingfrom adjacent the door sill elevation to the roof, said wall having aninner surface extending outwardly and upwardly to retain a protectivelining of furnace bottommaking material substantially throughout thesurface, the wall having an outer surface extending outwardly andupwardly in its lower portion and substantially vertically in its upperportion, the horizontal projection of the lower portion of the wallbeing not less than fifty percent of the elevation of the entire wall.

6. In an open hearth furnace, a hearth, a roof, a side wall extendingfrom adjacent the door sill elevation to the roof, said wall having aninner surface extending outwardly and upwardly to retain a protectivelining of furnace bottom-making material substantially throughout thesurface, the wall having an outer surface extending outwardly andupwardly in its lower portion and substantially vertically in its upperportion, the lower portion of the wall constituting not less than fortypercent nor more than eighty percent of the height of the wall, thehorizontal projection of the lower portion of the wall being not lessthan fifty percent of the elevation of the entire wall.

7. In an open hearth furnace, a hearth, a roof, at side wall extendingfrom adjacent the door sill elevation to the roof, said wall having an.

inner surface extending outwardly and upwardly to retain a protectivelining of furnace bottommaking material substantially throughout thesurface, the wall having an outer surface extending outwardly andupwardly in its lower portion and substantially vertically in its upperportion, the height of the outwardly and upwardly extending lower wallportion being at a maximum in the central portion of the furnace andgradually decreasing toward each end.

8. In an open hearth furnace, a hearth, a roof, a side wallextendingfrom adjacent the door sill elevation to the roof, said wall having aninner surface extending outwardly and upwardly to retain a protectivelining of furnace bottommaking material substantially throughout thesurface, the wall having an outer surface extending outwardly andupwardly in its lower portion and substantially vertically in its upperportion, the lower portion of the wall constituting not less than fortypercent nor more than eighty percent of the height of the wall, thehorizontal projection of the lower portion of the wall adjacent thecenter of the furnace being not less than fifty percent of the elevationof the wall, the height of the outwardly and upwardly extending lowerwall portion being at a maximum in the central portion of the furnaceand gradually decreasing toward each end.

GEORGE L. DANFORTH, J

